When doing wall-resolved LES (constant smagorinsky coeficient, also no wall modeling) in a flowfield which contains a solid wall..Does the grid sizes are required to be same in all directions near the wall..or it is just the normal direction in which grids should be more resolved??

The grid size does not have to be the same in all directions. The grid size in the spanwise and the streamwise direction can be larger than in the normal direction. Perhaps you can have a look in the literature, Physics of Fluids for example, many LES of channel flow have been reported there. By the way, if you use a Smag. model you have to be careful. Perhaps you have to force the subgrid-model to zero near the wall using a kind of demping function (van Driest) otherwise the subgrid contribution is not zero at the wall. This gives completely wrong results.